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Just swapped a ford 8 inch for a ford 9 inch rearend. I also installed 17x7 rims with 225/50 firestone firehawks tires. The rear fender edge keeps cutting into the tires when i hit a bump or dip in the road. The stock bump stops in the frame are about 8 to 10 inches away from rear end. How do i stop it from cutting into my tire.
 

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I had pretty much the same problem had car loaded the tool box lawn chairs me and my wife headed to car show never had a problem before. when we got back I installed a set of air shocks with 40 psi in them it raised the wheelwell clearance 1 inch they have not rubbed since . I have not noticed any difference in the ride.
 

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Unfortunately, air shocks mounted in the standard upper shock mount hole tend to now support some of the weight of the vehicle on the flimsy sheet metal holding the top of the shock. That sheet metal was not intended to hold the weight and is likely to fail. Your problem is due to the rim dimensions, more specifically the rim offset kicking the tire toward the wheel opening. You can roll the wheel well opening , or you can get rims with deeper offsets. Air shocks really should not be used to raise up the rear end. Both air shocks and longer rear spring shackles change the body geometry and effect the ride and safety of your car.
Best,
Al
 

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Maybe not strictly related to the original post...but i have air shocks on my 67. Are you saying that air shocks in general are not a good idea? The previous owner put them on.
 

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Did you get a 9 inch rear from a 65-66 mustang? 67-70 is two inches wider, one inch each side, 71-73 is 4 inches wider. Air shocks are bad, you cannot support the weight of the car on a quarter size piece of trunk sheetmetal. Bump stop won't prevent fender rub, what is the backspace of the 17x7? It should be 4.0-4.5 inches. If you used a 67-70 rear you need a 17x7 with 5.0-5.5" backspace.
 

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Zac, if the fenders are just slightly cutting/rubbing on the outer wall of your tires less than a couple inches from the top of the tire, the best option would be to get the inner lip of the fender rolled flat. There's a special tool that gently rolls the sheetmetal on the inside lip of the fender flat so that they don't cut in or rub. There's some folks on craigslist that advertise fender rolling services for $40 per car here in the L.A. area. But, if your offset is too far out or your wheels simply are too big and contact farther up than that lip, the fender rolling might not do you any good, and you'd need wheels with a different offset as Al Newman mentioned.

As far as air shocks- I agree they are just not good for our year mustangs because the sheet metal at the upper mounting hole is too thin. Over time, the shock can either dent or crack the metal from too much weight being carried at that point, and the sheet metal repair would be a huge deal if that happened and not worth the risk. I just replaced the air shocks on a 66 we just picked up and it had a slight bend at the holes. Fortunately the air shocks were at least 20 years old and had failed at some point, so they were no longer holding air and stopped putting that extra pressure on the metal that could have damaged it further.
 
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